Cca training diseases2

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Cca training diseases2

  1. 1. PLANT DISEASES CCA TRAINING BOB MULROONEYEXTENSION PLANT PATHOLOGIST UNIVERSITY OF DELAWARE
  2. 2. COMPETENCY AREA 2Management of Plant Diseases
  3. 3. Disease Identifications Symptomss Signs
  4. 4. SYMPTOMSsExternal and internal reactions or alterations of a plant as a result of a disease
  5. 5. Disease symptoms
  6. 6. SIGNSsThe pathogen (disease causing agent) or its parts or products seen on a host plant
  7. 7. Disease signs
  8. 8. CLASSIFY DISEASES BY PATHOGENs FUNGUSs BACTERIAs VIRUSs NEMATODE
  9. 9. EXAMPLESs WHEAT – TAKE-ALL caused by a FUNGUS – BARLEY YELLOW DWARF caused by a VIRUS
  10. 10. KNOW CONDITIONS THAT FAVOR DISEASE DEVELOPMENT FOR EACH DISEASEs CLIMATIC CONDTIONSs CROPPING PRACTICES
  11. 11. DETERMINE CONTROL MEASURES FOR EACH DISEASEs CULTURALs CHEMICAL
  12. 12. CULTURAL CONTROLSs ROTATIONs VARIETY (HYBRID) SELECTIONs PLANTING DATEs FERTILITY MANAGEMENTs TILLAGEs WEED CONTROL
  13. 13. DISEASE CONTROLs Some diseases may require a number of cultural controls or combination of cultural and chemical controls.
  14. 14. CORN DISEASES
  15. 15. Lesion nematode Symptom/Signs Lesions on rootss stunting of corn with uneven distribution in field
  16. 16. Lesion Nematode
  17. 17. Lesion nematode Control Methodss Rotation but few non-hosts grown.s Granular insecticide eg. Counter 15G
  18. 18. Maize dwarf mosaic (virus) Symptom/Signs Yellow stripes between veins on youngest leavess Stuntings Shortened internodess Sporadic distribution in field
  19. 19. Maize Dwarf Mosaic
  20. 20. Maize dwarf mosaic (virus) Conditions favoring developments Johnsongrass alternate hosts Aphids transmit to corn
  21. 21. Maize dwarf mosaic (virus) Control Methodss Resistant varietys Control Johnsongrass
  22. 22. Maize chlorotic dwarf (virus) Symptom/Signs Chlorosis (yellowing) severe on young leavess Some reddenings Severe stunting
  23. 23. Maize chlorotic dwarf (virus)
  24. 24. Maize chlorotic dwarf (virus) Conditions favoring developments Johnsongrass alternate hosts Leafhopper transmits to corn
  25. 25. Maize chlorotic dwarf (virus) Control Methodss Resistant varietys Control Johnsongrass
  26. 26. Northern corn leaf blight (fungus) Symptom/Signs Gray green elliptical (cigar-shaped) spots, 2-6 inches long on hybrids with no resistance.s Lesion size can be affected by hybrid.s Can be confused sometimes with Stewart’s wilt if certain resistance genes are present.
  27. 27. Northern Corn Leaf Blight (fungus)
  28. 28. Northern corn leaf blight (fungus) Conditions favoring developments Moderate temperature--65-85 Fs Long dew periodss Overwinters on plant debriss Windborne
  29. 29. Northern corn leaf blight (fungus) Control Methodss Resistant hybridss Crop rotations Tillage
  30. 30. Southern corn leaf blight (fungus) Symptom/Signs Spots on leaf smaller and more numerous than Northern corn leaf blights Spots vary in size and shape due to the genetic background of the hybrid.s Common race “O” produces tan, elongated spots between the veins that have limited parallel margins and possibly buff to brown borders.
  31. 31. Southern Corn Leaf Blight (fungus)
  32. 32. Southern corn leaf blight (fungus) Conditions favoring developments Warmer temperature--68-90 Fs High humiditys Overwinters on plant debriss Windbornes Splashed by water
  33. 33. Southern corn leaf blight (fungus) Control Methodss Resistant hybridss Crop rotations Tillage
  34. 34. Carbonum(Northern corn) Leaf Spot (fungus) Symptom/Signs Race 3 produces very narrow spots often resembling “beads on a string”.s Lesion (spot) type varies with the hybrids Often spreads after leaf tissue matures
  35. 35. Carbonum Leaf Spot
  36. 36. Carbonum(Northern corn) Leaf Spot Conditions favoring developments Moderate temperatures and high humiditys Spores are abundantly produced on old spots on mature leavess Minor importance, small impact on yield.
  37. 37. Carbonum leaf blight (fungus) Control Methodss Resistant hybridss Crop rotations Tillage
  38. 38. Gray leaf spot (fungus) Symptom/Signs Rectangular lesions with sharp parallel edges, restricted by veins with yellow margins Window pane look, and old lesions are opaque.s Early lesions are small necrotic spots with chlorotic halos.s Often symptoms are worse along the edges of fields
  39. 39. Gray Leaf Spot (fungus)
  40. 40. Gray leaf spot (fungus) Conditions favoring developments High humiditys Near water wayss Overwinters in residues Reduced tillage or no-till
  41. 41. Gray leaf spot (fungus) Control Methodss Resistant hybridss Tillage is recommended but is questionable where the disease is well established.s Rotation
  42. 42. Common Rust (fungus) Symptom/Signs Golden brown to cinnamon brown pustules on both sides of the leaf.
  43. 43. Common Rust (fungus)
  44. 44. Rust Conditions favoring developments Spores are wind blown from the south.s Moderate temperatures (61-80) and high humiditys Infections often occur in the whorl where moisture and humidity are high
  45. 45. Rust Control Methodss Resistant hybrids
  46. 46. Fusarium stalk rot (fungus) Symptom/Signs Cottony white mat of fungus at base of plant or at internodess Soft rotted stalks Red discoloration inside of stalks Lodgings Yield loss
  47. 47. Fusarium Stalk Rot
  48. 48. Fusarium stalk rot (fungus) Conditions favoring developments Reduced tillage or no-tills Fungus overwinters in crop residues Warm, wet conditionss Can enter through wounds or directly ( corn borer interaction)s Same organism causing scab in cereals
  49. 49. Fusarium stalk rot (fungus) Control Methodss Hybrid selections Tillages Proper fertilitys Rotations Early harvest
  50. 50. Fusarium ear rot (fungus) Symptom/Signs White fungus growing on kernelss Pink discolorations “Starburst” symptom on infected kernels
  51. 51. ‘Starburst pattern’ FusariumDiplodia Fusarium Giberella Fusarium Ear Rot
  52. 52. Fusarium ear rot (fungus) Conditions favoring developments Reduced or no-tills Fungus overwinters in crop residues Warm, wet conditionss Insect damage to ears Can produce mycotoxin “fumonison”
  53. 53. Fusarium ear rot (fungus) Control Methodss Tillages Proper fertilitys Rotations Early harvest
  54. 54. SOYBEAN DISEASES
  55. 55. Damping Off Symptom/Signs Seedlings fail to emerge or emerge then dies Seed or root is brown and decayed
  56. 56. Damping Off Conditions favoring developments Cool, damp conditions
  57. 57. Pythium Rhizoctonia Damping Off
  58. 58. Damping Off Control Methodss Seed treatment fungicidess Later planting dates Rotation
  59. 59. Phytophthora root rot (fungus) Symptom/Signs Poor growths Wiltings Brown discoloration on stems Rotted roots
  60. 60. Phytophthora Root Rot
  61. 61. Phytophthora root rot (fungus) Conditions favoring developments Poorly drained areass Heavy soilss Flooding
  62. 62. Phytophthora root rot (fungus) Control Methodss Resistant varietys Seed treatments using Apron, Apron XL, or Allegiance control the damping- off stage.
  63. 63. Rhizoctonia root rot (fungus) Symptom/Signs Seedlings emerge and dies Brown, red-brown, or red sunken lesion on roots or base of the seedling stem.
  64. 64. Rhizoctonia root rot (fungus) Conditions favoring developments Cool, damp conditionss Fertility, soil conditions and the amount of fungus in the soil can all influence the degree of infection.
  65. 65. Rhizoctonia root rot (fungus) Control Methodss Fungicide seed treatmentss Later planting date
  66. 66. Septoria leaf spot (Brown spot) Symptom/Sign s Irregular dark brown spots on unifoliate leaves progressing to trifoliates later in the season. s Infected unifoliate leaves turn brown and drop s Black fruiting bodies (pycnidia) of the fungus form in old spots.
  67. 67. Septoria leaf spot Conditions favoring developments Fungus overwinters on old infected plant debriss Unifoliate infection provides inoculum for later infections Warm, wet weather conditions especially later in the season influences brown spot in the canopy.
  68. 68. Septoria leaf spot Control Methodss Rotations Plant less susceptible varietiess Plow under crop residues
  69. 69. Charcoal rot Symptom/Signs Usually after midseason, plants appear stunted in irregular areas of the field.s Leaves may turn yellow and wilts Lower stem and taproot develop a gray to silvery discolorations Microsclerotia develop in epidermis on root and lower stem and inside pith resembling charcoal dust
  70. 70. Charcoal Rot
  71. 71. Charcoal rot Conditions favoring developments Low soil fertilitys Continuous cropping of soybeans.s Low soil moisture and hot temperatures increase disease severity.
  72. 72. Charcoal rot Control Methodss Plant later maturing varieties late group IV’s and group V’s.s Rotate with small grains, corn and sorghum for at least 3 years in severely infected fields.s Do not overplant, causes seedling stresss Good fertility practices
  73. 73. Sclerotinia white mold (fungus) Symptom/Signs Wilting and death of the upper leaves of the plants during early pod developments Often occurs in patches in low areass White mat of fungus on stem at nodes often seens Stem lesions often girldle the stem and the uper portions die and produce no pods.s Large sclerotia on stem and sometimes in pith
  74. 74. Sclerotinia White Mold
  75. 75. Sclerotinia white mold (fungus) Conditions favoring developments Cool, wet conditions that favor germination of sclerotia within the upper 2 inches of soil.s Narrow row spacings Dense canopy structures Fields with history of white mold on crops of peas, beans, and soybean
  76. 76. Sclerotinia white mold (fungus) Control Methodss Avoid planting soybeans after other susceptible crops such a peas, snap and lima beans, and sunflowers.s Choose varieties that are shorter, more open
  77. 77. Pod and stem blight (fungus) Symptom/Signs Rows of black fruiting bodies (pycnidia) on stems, petioles and pods late in seasons Infected seeds are decayed which leads to direct yield loss
  78. 78. Pod and Stem Blight
  79. 79. Pod and stem blight (fungus) Conditions favoring developments Disease of senescing soybeanss Seed infection favored by delayed harvests Warm, rainy weather during pod development through maturity.s Low potash levels favor more seed infection.
  80. 80. Pod and stem blight (fungus) Control Methodss Rotations Tillages Resistant varietys Maintain high level of potash fertility
  81. 81. Anthracnose Symptom/Signs Often appears in early reproductive stages on stems, petioles and pods as an irregularly shaped brown areas. Often resembles pod and stem blight.s Fruiting bodies of the fungus are randomly scattered on infected plants tissues and produce black spines called setae that can be seen.s Can produce cankers on petioles and stems causing severe defoliation.
  82. 82. Anthracnose
  83. 83. Anthracnose Conditions favoring developments Overwinters on debris and can infect seed.s Moist, warm weather during reproductive stages.s Plants are most susceptible from bloom to pod fills Need wet periods of 12 hours or more for infecton to occur.
  84. 84. Anthracnose Control Methodss Plant disease free seeds Plow down old soybean residuess Rotation
  85. 85. Soybean cyst nematode Symptom/Signs Stunted yellow plants in patches or large areass Poorly developed rootss Suppressed nodulations Lemon shaped cysts (females) on roots.
  86. 86. Soybean Cyst Nematode
  87. 87. Soybean Cyst Nematode
  88. 88. Soybean cyst nematode Control Methodss Resistant varietiess Rotation
  89. 89. Root knot nematode Symptom/Signs Stunted yellow plantss Knots (galls) on roots
  90. 90. Root Knot Nematode
  91. 91. Root knot nematode Control Methodss Resistant varietys Rotation
  92. 92. Soybean mosaic (virus) Symptom/Signs Puckered leavess Mosaic pattern of yellow and green on leavess Bleeding hilum on infected seed
  93. 93. Soybean Mosaic (virus)
  94. 94. Soybean mosaic (virus) Conditions favoring developments Seed borne diseases Aphid transmitted
  95. 95. Soybean mosaic (virus) Control Methodss Certified seeds Resistant variety
  96. 96. Tobacco Ringspot Virus Symptom/Signs Primarily seedborne at a low level in the fields This results in scattered infected plants.s Maturity is delayed so they remain green until killed by frosts Pods are underdeveloped, tops of plants have shortened internodes, and leaves are distorted
  97. 97. Tobacco Ringspot
  98. 98. Tobacco Ringspot Conditions favoring developments Nearby crops that may harbor the viruss Insect vectors are possible and disease is often found near the edges of fields.s Dagger nematode (Xiphinema) may cause a low level of transmission.
  99. 99. Tobacco Ringspot Control Methodss Planting virus free seed.
  100. 100. Wheat Diseases
  101. 101. Powdery Mildew (fungus) Symptom/Signs Irregular shaped yellow areas on leaf initaillys White powdery mass of fungus on upper surface of lower leavess Older PM colonies will have small brown to black sexual fruiting structures present late in the spring
  102. 102. Powdery Mildew
  103. 103. Powdery Mildew (fungus) Conditions favoring developments Optimal powdery mildew development occurs between 60- 72 F basically cool, wet conditionss High nitrogen fertilitys Dense stands of susceptible varietiess High humidity
  104. 104. Powdery Mildew (fungus) Control Methodss Resistant varietiess Rotation is of some value but limiteds Balanced fertilitys Fungicides (seed and/or foliar treatments)
  105. 105. Leaf rust (fungus) Symptom/Signs Orange-red pustules mostly on upper leaf surfacess Randomly scattered within the canopys Usually appears after heading
  106. 106. Leaf Rust
  107. 107. Leaf rust (fungus) Conditions favoring developments Temperatures from 59-72 F and free- moisture. Needs adequate rainfall.s Overwinters far souths Spores carried by wind
  108. 108. Leaf rust (fungus) Control Methodss Resistances Fungicides
  109. 109. Septoria leaf and glume blotch (fungus) Septoria nodorum Symptom/Signs Elongate lens-shaped lesions with yellow marginss Black fruiting bodies in center of lesion help distinguish from tan spot. Often found in orderly rows.s On the heads a brown to gray -brown discoloration occurs and pycnidia are found on the infected glumes
  110. 110. Septoria Leaf and Glume Blotch
  111. 111. Septoria leaf and glume blotch (fungus) Conditions favoring developments Optimal development is between 68-82 F wet, windy conditions.s Minimal wet periods of 6 hours, but mostly needs 16 hours of wetness.
  112. 112. Septoria leaf and glume blotch (fungus) Control Methodss Fungicidess Tillage
  113. 113. Scab (fungus) Symptom/Signs Bleached spikelets on part or all of wheat heads Pink or orange spore masses may be seen at the base of infected spikelets during periods of high humiditys Infected heads are sterile or contain white shriveled grains Same as Fusarium on corn (mycotoxins)
  114. 114. Scab
  115. 115. Scab (fungus) Conditions favoring developments Spores from corn, wheat and grass residue spread to flowering wheat under warm, wet conditions.s Temperatures between 77-86 F and continous moisture at flowering are most favorable for epidemics.
  116. 116. Scab (fungus) Control Methodss Tillage prior to plantings Rotation (limited value in areas with intense no-till or reduced tillage corn production)s No resistance
  117. 117. Take-all (fungus) Symptom/Signs Infected plants are stunted and ripen prematurelys Best identified at heading by stunted growth in patches and heads are bleached white and often steriles Black lesions at base of crown under the lowest leaf sheaths Plants pull easily from the soil from extensive rot rot.
  118. 118. Take-all
  119. 119. Take-all
  120. 120. Take-all (fungus) Conditions favoring developments Continuous wheat productions High pH, poorly drained soils or wet years
  121. 121. Take-all (fungus) Control Methodss Rotations Maintain good fertility levelss No good resistant varietiess Control grassy weeds before cropping to wheat
  122. 122. Barley yellow dwarf (virus) Symptom/Signs Ambiguous often look like nutritional disorderss Fall infection results in patches of yellow, stunted plants. Spring infections usually result in plants of varying heights and yellow or purple colored flag leaves after head emergences Occurs in patches of field where aphid vectors feed
  123. 123. Barley Yellow Dwarf
  124. 124. Barley yellow dwarf (virus) Conditions favoring developments Transmitted by aphidss Cool, moist conditions (50-65 F)s Early planted fields attractive to aphidss Mild winter with aphids
  125. 125. Barley yellow dwarf (virus) Control Methodss Tolerances Later planting dates Control aphids
  126. 126. Wheat spindle streak mosaic (virus) Symptom/Signs Non-distinct yellow streaks can be confused with early stage powdery mildews Often produces yellow-green mottling, dashes and streaks. The streaks often have tapered ends forming spindles.s Entire field affected--not patchy. Low spots in field can have more severe symptoms.
  127. 127. Wheat Spindle Streak
  128. 128. Wheat spindle streak mosaic (virus) Conditions favoring developments Soil borne viruss Transmitted by fungus, in the fall.s Cool weather (46-53 F) produces the most symptomss “Disappears” as temperatures increase
  129. 129. Wheat spindle streak (virus) Control Methodss Resistant varietys Rotation of some values Later plantings Poultry manure may decrease disease incidence
  130. 130. Loose Smut (fungus) Symptom/Sign s Black smutted heads on wheat
  131. 131. Loose Smut (fungus) Control Methodss Fungicide seed treatments Plant certified seed
  132. 132. Alfalfa Diseases
  133. 133. Phytophthora root rot (fungus) Symptom/Signs Poor growths Wiltings Brown discoloration on stems Rotted roots
  134. 134. Phytophthora Root Rot
  135. 135. Phytophthora Root Rot
  136. 136. Phytophthora root rot (fungus) Conditions favoring developments Cool, wet conditionss Poorly drained soils
  137. 137. Phytophthora root rot (fungus) Control Methodss Select well drained sitess Break up compacted soils to enhance drainages Plant resistance varietiess Use Apron seed treatments to avoid seedling damping-off
  138. 138. Anthracnose (fungus) Symptom/Signs Wilted stemss Diamond shaped lesions on lower stems Lesion gray with red margins Scattered in the fields Infected stems with characteristic diamond shaped lesion will also produce a typical shepard’s crook
  139. 139. Anthracnose
  140. 140. Anthracnose (fungus) Conditions favoring developments Warm, humid conditionss Late summer/ early fall weather can be very favorable for infection
  141. 141. Anthracnose (fungus) Control Methodss Resistant varietys Clean harvesting equipment before first cutting and when going from a known infected fields to a healthy field.
  142. 142. Sclerotinia crown rot (fungus) Symptom/Signs Fall- planted alfalfa dies in spring during cool, wet conditions.s Cottony web-like growth on stems and crownss Stems turn brown, then soft and mushy then disintegrate.s Black fruiting bodies (Sclerotia) on stem
  143. 143. Sclerotinia Crown Rot
  144. 144. Sclerotinia Crown Rot
  145. 145. Sclerotinia crown rot (fungus) Conditions favoring developments Infection occurs in falls Plants die in cool, wet springs Favored by late summer early fall plantings Planting into clovers
  146. 146. Sclerotinia crown rot (fungus) Control Methodss Spring planting dates Deep plowing to bury sclerotias No resistance
  147. 147. Leaf spots (fungus)-Common Lepto Symptom/Signs Spots on leavess New growth most affected
  148. 148. Leaf Spots
  149. 149. Leaf spots (fungus)-Common Lepto Conditions favoring developments Cool, moist season
  150. 150. Leaf spots (fungus)-Common Lepto Control Methodss Early harvest
  151. 151. Spring blackstem (fungus) Symptom/Signs Black spots on lower leaves, petioles, stemss Entire stem black--first cutting problem
  152. 152. Spring Blackstem
  153. 153. Spring blackstem (fungus) Conditions favoring developments Cool, moist early season and again in falls Heavy dew or rain
  154. 154. Spring blackstem (fungus) Control Methodss Early cuttings Plant moderately resistant cultivars
  155. 155. Verticillium wilt (fungus) Symptom/Signs Scattered infected stemss Early symptoms include V-shaped chlorosis at leaflet tipss Not all stems on the same plant infected initiallys Internal root tissue is often brown, but it is not a dependable diagnostic feature.
  156. 156. Verticillium Wilt
  157. 157. Verticillium Wilt
  158. 158. Verticillium wilt (fungus) Conditions favoring developments Introduced on seed usuallys Could be disseminated in manures Insects can can serve as vectorss Can spread within the field during cutting
  159. 159. Verticillium wilt (fungus) Control Methodss Plant clean seed free of debriss Plant resistant varietiess Disinfestation of cutter bars and equipment
  160. 160. Most Common Symptoms of Nematode InjuryField Symptomss Stunting and sometimes yellowing of plants in patches of varying sizes Not definitive, need to look at rootsPlant Symptoms and Signss Galls, cysts, lesions or dead areas on roots
  161. 161. FUNGICIDE CLASSIFICATIONs PROTECTANT – Forms a protective barrier on the plant surface that prevents spore germination eg. Dithane, Bravo, thirams SYSTEMIC – Moves in the plant from point of application across the leaf or into new growth. Can move from roots to above ground parts. Prevents spores from germinating or kills them soon after germination. Eg. Tilt, Baytan, Raxil, Quadris, Ridomil.s ERADICATIVE (Curative)- kills fungus already present. Some systemic fungicides have some curative activity
  162. 162. TREATMENT THRESHOLDS FOR FUNGICIDE APPLICATIONs Thresholds are available for making spray decisions for wheat in the mid-Atlantic region.s Use stage of development and amount of disease present to determine need for an application.

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